Eh, I have them, having acquired them as parts of lots at auction. They're OK, but really don't grab me. They mostly sit on a shelf. I don't find them especially useful. I think the format is the primary issue, along with some of the worst aspects of 2e: lots and lots of whitespace. For the most part, they feel like products made up entirely of filler.

I have it and I like it because they contain in-character descriptions of some lands of Faerun but I suppose you can easily live without also because it quite focused on just some lands.
Index has Cormanthor, Anauroch, Sea of Fallen Star coasts, Cormyrean Marshes, Stonelands, Thunder Peaks, Thar and Settled Lands, so is most the central lands.
Appendix 1 is about two sites, Battle of Bones and Hills of Lost Souls
Appendix 2 has the High Moor and the Serpent Hills. The appendixes are different products, not included in the boxed set.

If you plan to run adventures in the regions covered by the individual sections, I would highly recommend them. If not, they might be useful to draw on for running similar regions on other worlds, but otherwise probably not that useful.

Eh, I have them, having acquired them as parts of lots at auction. They're OK, but really don't grab me. They mostly sit on a shelf. I don't find them especially useful. I think the format is the primary issue, along with some of the worst aspects of 2e: lots and lots of whitespace. For the most part, they feel like products made up entirely of filler.

Excessive whitespace in later 2nd Edition products...along with super large typefaces (compared to the PHB/DMG) is what made me start to feel I was being ripped off by TSR. That's why I gave up on D&D...for a while.

But, I think I would look at those products with different eyes now...wanting to pay less for them, rather than avoid them entirely.

I have it and I like it because they contain in-character descriptions of some lands of Faerun but I suppose you can easily live without also because it quite focused on just some lands.
Index has Cormanthor, Anauroch, Sea of Fallen Star coasts, Cormyrean Marshes, Stonelands, Thunder Peaks, Thar and Settled Lands, so is most the central lands.

It's interesting that you have a reaction to these books that is almost the opposite of Night Druid's. I'm guessing that must mean that the book works for a certain type of playstyle...rather than being obviously good or bad for everyone. I wonder if they would work for me.

Excessive whitespace in later 2nd Edition products...along with super large typefaces (compared to the PHB/DMG) is what made me start to feel I was being ripped off by TSR. That's why I gave up on D&D...for a while.

But, I think I would look at those products with different eyes now...wanting to pay less for them, rather than avoid them entirely.

I'm not entirely sure what the target market of the Ecology books were. As a whole they seemed to be entirely filler material. Maybe as a series of Dragon articles they might have worked, or combined into a single book (the boxed set + the two add-ons). To me they just lacked meat. Maybe if they had been attached to adventures for the areas in question. But lots of whitespace, huge typefaces, and a rather thin page-count makes them a dubious purchase to me.

If you plan to run adventures in the regions covered by the individual sections, I would highly recommend them. If not, they might be useful to draw on for running similar regions on other worlds, but otherwise probably not that useful.

I want to improve my Realms-fu in general, but the thing I would be most likely to do with them, in-game, is use them to inspire the vibe for somewhere like one of the Tears of Selûne or an area on one of the other celestial bodies of Realmspace (that is fairly similar to Toril in some respects).

I'm aiming to have (some) new stuff that "feels" familiar (as well as other stuff that feels different).

Excessive whitespace in later 2nd Edition products...along with super large typefaces (compared to the PHB/DMG) is what made me start to feel I was being ripped off by TSR. That's why I gave up on D&D...for a while.

But, I think I would look at those products with different eyes now...wanting to pay less for them, rather than avoid them entirely.

I'm not entirely sure what the target market of the Ecology books were. As a whole they seemed to be entirely filler material. Maybe as a series of Dragon articles they might have worked, or combined into a single book (the boxed set + the two add-ons). To me they just lacked meat. Maybe if they had been attached to adventures for the areas in question. But lots of whitespace, huge typefaces, and a rather thin page-count makes them a dubious purchase to me.

Well it's a single book now on DMs Guild. They have it for $19.99 USD!

I suppose they are not really so useful to you, unless you find them at a very low price. I found it interesting because they contain in-character descriptions of place by adventurers/travellers. So you can make adventures and campaigns with them, but it needs quite some work from the DM. Still I had not the chance yet to use them, but I hope to do so one day. They are mostly flavour and setting, and I like that, but I cannot say they have been extremely useful to me, for now

I'm not sure what "filler material" means, but the products IMO would be quite useful to anyone who wants to make a campaign set in the region come alive. Sure, other than some occasional stats for local unique fauna/monsters and random encounter charts, there isn't a lot of rules/crunch information, but the other information is pretty good. Want to know about tribes of humanoids in the region? What some of the known dragons are in the region? How some of the monsters survive, what they eat, etc.? This is for you. There are also plenty of adventure ideas. I found it really interesting when I got it, and wish they'd produce more material like this.

If you want fully-fledged adventures, if you want new character options, magic, gameplay stuff, or things that you can drop directly into a game, then yeah, it's not not really what you're looking for. If you want to know more about these specific regions of Faerun, then yeah, go for it.